Combines and harvesters are typically used to harvest grain and cereal crops. In addition to severing the crop plant from the ground, combines also thrash the severed plants to separate the grains from the stalks, husks, cobs and other residue. After the thrashing is performed on the plants, the products of this process are conveyed to a sifting, shelling and husking process in which the grain is separated from the residue. The residue is usually conveyed to the rear of the combine and is distributed back on the ground by a spreader apparatus located at the rear of the combine.
The grain, after being sifted and separated, is conveyed to a storage bin on the combine. Usually a conveyor is used because the storage bin is located above the separating area of the machine. The grain at this point typically contains high moisture content. With almost all grains harvested, some drying is necessary prior to storage, sale and delivery. Without drying, the grain is much more prone to bacteria growth and rotting. It also reduces the probability of later hot spot formations during subsequent storage of the grain, which reduces the possibility of fires.
Current techniques require the grain dryer to be placed next to the storage bins or silos as they are sometimes referred to. Grain drying is costly not only in fuel costs, but also for the equipment that is needed to support the drying operation. Additionally labor and transportation costs must be included in the overall cost of drying the grain. There is also the down time spent in waiting for the dryer to catch up with the grain harvested by the combine. At this time, the combine can harvest faster than the grain can remove moisture from the grain. This can be extremely costly if weather problems arise. There is only a limited optimum harvesting time and to maximize efficiency, it is necessary to harvest, dry and store as much of the crop as possible in the short time frame allowed.
In a conventional system, the steps taken by the farmer after the grain has been harvested and is ready to be transported to the grain center for drying and storage are as follows. First, the grain is off-loaded into the farm receptacle and is then transported to the grain center. Second, the receptacle is off-loaded into a holding bin via a conveyor from a dumping pit. Third, the grain is tested for moisture content and is then transferred to the dryer. Fourth, the grain is dryer and transferred to a holding bin where it is again tested for moisture to be readied for storage or delivered for immediate sale. Fifth, the dried grain is conveyer into final storage bins, or loaded into vehicles for delivery.
These steps are accomplished with the use of conveyors and other grain handling equipment. The costs involved are substantial. The down time lost waiting for the dryer to catch up after the first days harvest can amount to thirty to fifty percent of the daylight hours on a daily basis.
The cost to construct a normal drying process as known and practiced today can cost upwards of a quarter of a million dollars depending on the amount of grain to be processed. In additions to being inefficient in the drying process, it is also inefficient in its energy consumption. As the amount of moisture to be removed from the grain increases, the inefficiency of the system results in tremendous waste.
For example shelled corn must not have moisture content of more than 15 percent when it is stored, or it faces the possibility of spoilage. When severed from the ground, however, corn kernels have moisture content of between 20 and 24 percent. Under the most favorable circumstances, the kernels must be dried to eliminate at least five percent of their moisture content. Under the worst circumstances, they must be dried to eliminate nine percent. At present energy prices, costs for drying one bushel of shelled corn to a point where it can be stored are at least 6.5 cents per each percentage point of moisture content which must be eliminated. The costs, therefore, for drying one bushel of shelled corn would range between thirty-two and fifty-eight cents. When considering that six to seven billion bushels of corn are harvested annually, one can see that an extremely significant overall cost is involved. Even slight savings per bushel will result in tremendous overall savings.
Various types of grain dryers have been invented in the past. For example U.S. Pat. No. 1,554,780 issued to Berrigan et al. for Drier and Process of Drying illustrates a drier used to dry solid material removed from sludge. The material falls through a series of flames for drying. A series of inclined baffle plates direct the flow of the solid material. The flames used in this patent would burn the grain if applied to a grain drying process
U.S. Pat. No. 3,058,235 issued to Morris et al. for Vibratory Heat Transfer Apparatus. This patent illustrates a box like frame supported on a series of springs. A vibrating force is applied to the frame causing it to vibrate. A plurality of sloping pervious trays is mounted in the box. The material to be dried is introduced through an entrance chute and passes over each tray as it travels back and forth from one tray to the next lower tray. To minimize the escape of the treating gas a flexible curtain is used. The gas flows into manifolds located on the sides of the box and through ports into the spaces directly below the porous trays. The trays are enclosed on the sides and bottoms. The gas, after passing through the trays, is exhausted. Only one temperature of heated air is used to dry the grain.
U.S. Pat. No. 3,158,448 issued to Wallin et al. for Drier With Gas-Moved Bed of Material discloses a conveyor system in which gas flows through a porous conveyor supporting a bed of material which is to be dried. The patent discloses an improved means for cleaning the air duct
U.S. Pat. No. 3,771,947 issued to Cook for Apparatus and Method for Heating Flowable Material is directed to a method of making asphalt paving materials. It uses high temperature gas injected at a high velocity to fluidize the particles as they drop though a drop zone. It is not adaptable to a grain drying application, as it would burn the grain. It also does not use a vibrating conveyor or a series of heating and cooling steps.
U.S. Pat. No. 3,793,745 issued to Myers for Aggregate Dryer moves aggregate upwardly from the bottom of the housing to the top. A series if conveyors does the upward movement in a conventional manner. Heaters dry the aggregate as it moves upward.
U.S. Pat. No. 4,125,945 issued to Westelaken for Multiple Stage Dryer with Intermediate Steeping illustrates a grain drying tower in which the grain passes from top to bottom by gravity flow. There are intermediate drying zones, which end in a cooling zone
U.S. Pat. No. 4,237,622 issued to Francis for Dryer Using Vibratory Feeding designed for drying small industrial parts. The parts move along a vibrating helical ramp. There is an air plenum, which continuously introduces heated air onto the ramp
None of the devices disclosed in the patents discussed above have come close to achieving the desired goals of a low cost dryer that is compact in size, efficient to operate, and can be either a stand alone unit or incorporated with a combine or harvester. Applicant's invention has achieved all of these goals. Furthermore it has reduced the cost of drying a bushel of corn by at least fifty per cent depending on the amount of moisture reduction.
Applicant's invention utilizes a unique method and apparatus for drying grain or other similar products, which require moisture reduction. The grain is introduced into the top of the dryer usually by means of a conveyor. The moisture and temperature is sensed to determine if additional moisture must be removed. The grain is moved through a series of partially enclosed vibrating conveyors. The magnitude of vibration determines the speed of the grain. The conveyors are arranged in an alternating, overlapping, stair step configuration to promote a compact design with the dried grain exiting near the original combine grain transfer point. The conveyors all have porous bases to allow airflow up through the conveyor. A heat source supplies heated air to alternate conveyors. Ambient or cool air is supplied to the other alternate conveyors such that a cool air conveyor separates each heated air conveyor. The heat and humidity is monitored as the grain moves along each conveyor. A control system controls the temperature of the heated air, the vibration of the conveyors, and the resulting speed of grain movement. The entire apparatus can be mounted in conjunction with a combine or harvester or built as a stand-alone unit.